In this specification where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge, or otherwise constitutes prior art under the applicable statutory provisions; or is known to be relevant to an attempt to solve any problem with which this specification is concerned.
Analytical techniques can provide powerful tools for testing of a wide variety of samples, such as, drinking water, waste water, and biological fluids such as blood and urine. One category of such techniques rely upon electrochemical reactions of analytes. A typical electrochemical cell shown in FIG. 1 comprises a container 110, a working electrode 120, a counter electrode 130, and a reference electrode 140. The three electrodes are immersed in an analyte solution 150 in the container 110. The reference electrode 140 provides a fixed voltage relative to the analyte solution 150. During use, a voltage signal is applied to the working electrode 120 relative to the reference electrode 140; electrical current flows between the working electrode 120 and the counter electrode 130; and no electrical current flows through the reference electrode 140. A common electrochemical testing technique is cyclic voltammetry (CV), in which voltage on the working electrode 120 is ramped linearly versus time and a peak appears in the current between the working electrode 120 and the counter electrode 130 when any analyte is reduced or oxidized. The current is often limited by diffusion of chemical species to the surfaces of the working electrode 120 and the counter electrode 130. In conventional electrochemical cells, the physical distance between the electrodes is on the order of centimeters. Diffusion of the chemical species over such distance limits the temporal and quantitative sensitivities of these conventional electrochemical cells.
While certain aspects of conventional technologies have been discussed to facilitate disclosure of the invention, Applicants in no way disclaim these technical aspects, and it is contemplated that the claimed invention may encompass one or more of the conventional technical aspects discussed herein.